The present invention relates to a positive working light-sensitive composition which makes it possible to form a presensitized plate for use in making a lithographic printing plate (hereunder referred to as "PS plate"), proof sheets for process printing, figures for overhead projectors or fine resist patterns required for making integrated circuits (IC) of semiconductor elements.
As so-called positive working light-sensitive materials which are made soluble by irradiating with actinic rays, for instance, in making lithographic printing plates, there have been known o-quinonediazide compounds and these compounds have practically been utilized widely for preparing PS plates or the like. Such o-quinonediazide compounds are disclosed in various publications inclusive of U.S. Pat. Nos. 2,766,118; 2,767,092; 2,772,972; 2,859,112; 2,907,665; 3,046,110; 3,046,111; 3,046,115; 3,046,118; 3,046,119; 3,046,120; 3,046,121; 3,046,122; 3,046,123; 3,061,430; 3,102,809; 3,106,465; 3,635,709; and 3,647,443.
These o-quinonediazide compounds are decomposed by irradiation with actinic rays to form 5-membered carboxylic acids and they are thus made alkali-soluble. In these applications of the light-sensitive material, such properties of the compounds are utilised. However, their light-sensitivity is insufficient. This problem arises because it is difficult to optically sensitize the o-quinonediazide compounds and their quantum yield essentially never exceeds 1. Further, light wavelength for exposure is fixed and light sources are limited. It is difficult to impart safety under white light. In addition, the absorption of light in Deep-UV region is great and thus it is not suitable for applications in which light of short wave length is used to enhance the resolution of a photoresist.
Many attempts have been made to improve the light-sensitivity of light-sensitive compositions containing o-quinonediazide compounds. For instance, examples of such attempts are disclosed in Japanese Patent Publication for Opposition Purpose (hereunder referred to as "J.P. KOKOKU") No. Sho 48-12242, Japanese Patent Un-examined Publication (hereunder referred to as "J.P. KOKAI") No. Sho 52-40125 and U.S. Pat. No. 4,307,173.
Recently, there have been proposed some positive working light-sensitive compositions free of o-quinonediazide compounds. One example thereof comprises a polymeric compound having o-nitrocarbinol ester groups as disclosed in J.P. KOKOKU No. Sho 56-2696. However, such a composition does not provide high sensitivity for the same reasons as those discussed above in connection with o-quinonediazide compounds.
On the other hand, as pattern-forming methods used in making electronic parts such as semiconductor elements, magnetic bubble memories and integrated circuits, there have been widely employed methods in which photoresists sensitive to ultraviolet and visible rays are used. The photoresists are classified into two groups, one of which is negative working type ones whose exposed portions are made insoluble in a developer by irradiating with light, and the other of which is positive working ones whose exposed portions are, on the contrary, made soluble in a developer. The negative working type ones are superior in sensitivity to the positive working ones and adhesion to a substrate and resistance to chemicals required in wet etching are also excellent. Therefore, the use of negative working resists is one of the mainstreams of photolithography. However, the line width and the distance between lines of patterns become smaller as the degree of integration of semiconductor elements and the packaging density thereof are increased. In addition, dry etching techniques have been adopted as a means for etching substrates. Thus, the photoresists should have high resolution and high resistance to dry etching. For this reason, positive working photoresists are mainly utilized recently. In particular, there have been exclusively used alkali developable positive working photoresists mainly composed of alkali-soluble novolak resins as disclosed in J. C. Strieter, Kodak Microelectronics Seminar Proceedings, 1976, p. 116, since they are excellent in sensitivity, resolution and resistance to dry etching.
However, it is required to make much smaller size of patterns to thus achieve much higher packaging density and degree of integration accompanied by the recent increase in multifunctionality and high functionality of electronic devices.
Under such circumstances, there have been proposed light-sensitive compositions comprising a combination of a conventional o-quinonediazide light-sensitive material and a silicone polymer such as polysiloxane or polysilmethylene which is made alkali-soluble, for instance, those disclosed in J. P. KOKAI Nos. Sho 61-256347, Sho 61-144639, Sho 62-159141, Sho 62-191849, Sho 62-220949, Sho 62-229136, Sho 63-90534 and Sho 63-91654. Further, a light-sensitive composition comprising a combination of a polysiloxane/carbonate block copolymer and an effective amount of an onium salt is disclosed in J. P. KOKAI No. Sho 62-136638. However, it is very difficult to produce these polymers owing to the operation of making them alkali-soluble. Further, the resistance to aging of these polymers is not sufficient.